The present invention relates to a method for making light-emitting or light-receiving semiconductor device wherein a pn junction and a pair of electrodes are formed on a spherical or cylindrical semiconductor with a pair of flat surfaces. These light-emitting or light-receiving semiconductor devices can be used in various applications such as in solar batteries, light-emitting devices, and optical semiconductor media.
Research has been done in technologies wherein a pn junction separated by a diffusion layer is formed on the surface of a small, spherical semiconductor element formed from p-type or n-type semiconductors. Multiple spherical semiconductor elements of this type are connected in parallel to a shared electrode to be used in solar cells and optical semiconductor photocatalyist.
U.S. Pat. No. 3,998,659 discloses an example of a solar cell. A p-type diffusion layer is formed on the surface of an n-type spherical semiconductor, and multiple spherical semiconductors of this type are connected to a shared electrode film (positive electrode) while the n-type cores of these spherical semiconductors are connected to a shared electrode film (negative electrode).
In U.S. Pat. No. 4,021,323, p-type spherical semiconductor elements and n-type spherical semiconductor elements are arranged in a matrix and connected to a shared electrode film. These semiconductor elements are also placed in contact with an electrolytic fluid. This results in a solar energy converter where electrolysis of the electrolyte takes place when illuminated with sunlight. U.S. Pat. Nos. 4,100,051 and 4,136,436 present similar solar energy converters.
As presented in PCT gazettes WO98/15983 and WO99/10935, the inventor of the present invention proposed a light-emitting or light-receiving semiconductor element wherein a diffusion layer, a pn junction, and a pair of electrodes are formed on a spherical semiconductor made from a p-type semiconductor and a n-type semiconductor. These multiple semiconductor elements of this type can be connected in series, and these series can be connected in parallel to form solar cells, photocatlyst devices involving the electrolysis of water and the like, as well as various types of light-emitting devices, color displays, and the like.
The semiconductor elements used in this semiconductor device are small particles with diameters of 1-2 mm. The pair of electrodes are formed at two apexes positioned on either side of the center of the spherical semiconductor element. However, the various issues remained with regard to the manufacture of the semiconductor element disclosed in these PCT gazettes.
In forming the pair of electrodes (positive and negative electrodes) on the spherical semiconductor device, the positions at which to form the electrodes are difficult to determine. Also, the spherical semiconductor devices tend to roll around, making handling difficult. This makes arranging multiple semiconductor devices difficult.
Also, once the pair of electrodes is formed, it is not possible to identify which electrode is the positive electrode and which electrode is the negative electrode. Thus, identification of the positive and negative electrodes is difficult when multiple semiconductor elements are arranged to connect them in series. Identifying the electrodes requires experience, leading to reduced efficiency. Errors in positive and negative electrode identification will lead to defective products.
The object of the present invention is to provide a spherical light-emitting or light-receiving semiconductor device that is formed with a pair of flat surfaces and that does not roll around easily. Another object of the present invention is to provide a spherical or cylindrical light-emitting or light-receiving semiconductor device in which a pair of electrodes is formed on a pair of parallel flat surfaces. Yet another object of the present invention is to provide a spherical or cylindrical light-emitting or light-receiving semiconductor device with an identifiable pair of electrodes. Yet another object of the present invention is to provide a method for making the light-emitting or light-receiving semiconductor devices described above.
A light-emitting or light-receiving semiconductor device according to the present invention includes: a roughly spherical semiconductor element formed from a p-type or n-type semiconductor, the semiconductor element being formed with parallel first and second flat surfaces at ends on either side of a center thereof; a roughly spherical pn junction formed on a surface section of the semiconductor element including the first flat surface; and first and second electrodes disposed on the first and the second flat surfaces respectively and connected to ends of the pn junction (claim 1).
It would be desirable an average diameter of the first and the second flat surfaces to be smaller than a distance between the flat surfaces (claim 2). It would be desirable for the first and the second flat surfaces to be formed with different diameters (claim 3). It would be desirable for the semiconductor element to be made from a spherical semiconductor element (claim 4).
According to another aspect, the present invention provides a light-emitting or light-receiving semiconductor device including: a cylindrical semiconductor element formed from a p-type or n-type semiconductor, the semiconductor element being formed with parallel first and second flat surfaces at ends of the element and perpendicular to an axis thereof; a pn junction formed a surface section of the semiconductor element including the first flat surface; and first and second electrodes disposed on the first and the second flat surfaces respectively and connected to ends of the pn junction (claim 5).
It would be desirable for an average diameter of the first and the second flat surfaces to be smaller than a distance between the flat surfaces (claim 6).
In the semiconductor devices in claim 2 or claim 6, the following configurations would be desirable. The semiconductor element is a single crystal semiconductor (claim 7). The semiconductor element is a silicon semiconductor (claim 8). The semiconductor element is a mixed-crystal silicon and germanium semiconductor (claim 9). The semiconductor element is a compound semiconductor formed from GaAs, InP, GaP, GaN, or InCuSe (claim 10). The semiconductor element is formed from a p-type semiconductor; the diffusion layer is formed from a n-type diffusion layer; a p-type diffusion layer is formed on the second flat surface; and a second electrode is disposed on a surface of the p-type diffusion layer (claim 11). The semiconductor element is formed from a n-type semiconductor; the diffusion layer is formed from a p-type diffusion layer; a n-type diffusion layer is formed on the second flat surface; and a second electrode is disposed on a surface of the n-type diffusion layer (claim 12).
A method for making a light emitting or light-receiving semiconductor device according to the present invention includes: a first step for making a spherical semiconductor formed from a p-type or n-type semiconductor; a second step for forming a first flat surface at an end of the semiconductor element; a third step for forming on a surface section of the semiconductor element including the first flat surface a diffusion layer from a conductor different from the semiconductor element and a roughly spherical pn junction with the diffusion layer; a fourth step for forming a second flat surface by removing the diffusion layer, the flat surface being parallel to the first flat surface and positioned opposite from the first flat surface of the semiconductor element; and a fifth step for forming a first and a second electrode on the first and the second flat surface respectively, the first and the second electrodes being connected to ends of the pn junction (claim 13).
A method for making a light emitting or light-receiving semiconductor device according to the present invention includes: a first step for making a spherical semiconductor formed from a p-type semiconductor; a second step for forming parallel first and second flat surfaces on either end of a center of the semiconductor element; a third step for forming on a surface section of the semiconductor element including the first flat surface and the second flat surface a n-type diffusion layer and a roughly spherical pn junction on the diffusion layer; and a fourth step for forming a first and a second electrode on the first and the second flat surface respectively, the first and the second electrodes being connected to ends of the pn junction (claim 14).
It would be desirable in the fourth step, for a small piece of Al, AuGa, or AuB to be placed in contact with the second flat surface and heated and fused to form a p-type recrystallized layer passing through the diffusion layer and a second electrode continuous with the recrystallized layer (claim 15).
A method for making a light emitting or light-receiving semiconductor device including: a first step for making a cylindrical semiconductor formed from a p-type or n-type semiconductor and forming parallel first and second flat surfaces at ends of the semiconductor element, the surfaces being perpendicular to an axis thereof; a second step for forming on a surface section of the semiconductor element a diffusion layer from a conductor different from the semiconductor element and a pn junction with the diffusion layer; and a third step for forming a first and a second electrode on the first and the second flat surface respectively, the first and the second electrodes being connected to ends of the pn junction (claim 16). It would be desirable in the third step, for a small piece of Al, AuGa, or AuB to be placed in contact with the second flat surface and heated and fused to form a p-type or n-type recrystallized layer passing through the diffusion layer and a second electrode continuous with the recrystallized layer (claim 17).